Friday, 24 June 2011

More on time-based GIS

Time-lapse GIS helps clear the clutter of a quarter million points of ship sailings from captain's logs from 1662 to 1855 re-posted last week. As an at-home project I previously split the data into arbitrary half-century time slices to better visualise it all. But that interfered with seeing trends across the span of data.

KNMI's CLIWOC project was a monumental task, fraught with difficulties not the least of which was simply running out of time to aggregate disparate data sources and formats. as detailed in my original posting. But now I reset all the geographic data into a single feature class in a database, such that we can traverse it by time, nationality, port of origin and destination etc., and thus give full justice to CLIWOC's atlas.

Displaying all 252,917 points look of course rather messy, like my daughter's finger painting as she traced imaginary voyages on her globe - which she did, not the finger painting! - the joys of sharing projects at home...

The same for 1762 however cleans up the map to show the Dutch triangular trade in the West Indies in yellow, as well as the British East India Company routes in blue, also in blue far to the north the Hudson Bay Company route, but not yet the Dutch East India ones.

Best of all is the time-slider that allows to interactively slide back &forth to see the trends, or even play it all in one go. See the end of my latest posting in for brief explanations. Also how GIS helps find missing data and point to further research.

Roger Tomlinson once told me casually - sipping tea and lemon awaiting the return flight from Tyumen to Moscow five or so years ago - carefully scrutinising the data helps us see both its strengths and weaknesses. Words never spoken truer, with another tool-kit to help us along! And as I said earlier this is but the spatial data, the tip of the iceberg if you add CLIWOC weather / climate data, to follow...